Any DCS World keys purchased from other sources are invalid and are simply trying to re-sell keys that are bound to other users or purchased through fraud. Such sites include Kinguin, CDExpress and G2A.

If you purchase DCS World keys from these sites, we cannot help you. We suggest you contact these sites for a refund.

I thought about this, disappointed at not being able to do any kind of radio navigation with the P-51. It would be fun to have a 'restored' P51 with some modern navigation instruments. But

a) This really shouldn't be a DCS priority.
b) If just flying around for fun, a real substantial terrain (preferably worldwide) is required. Caucasus gets old quick.

A worldwide terrain simply isn't happening unless free user made terrains are allowed. I remember flying MSFS ca 1996, I remember the insane amount of user made terrain that was available. You could choose multiple terrains for the same area, go with the terrain maker you liked best.